1. Field of the Invention
The present invention relates generally to electronics packaging and interconnection systems.
2. Description of the Related Art
A variety of electronic interconnection systems have been proposed for embedded microprocessor applications, i.e., applications in which the microprocessors are preprogrammed for a specific task and buried within the equipment that they serve. An exemplary system includes a "fat tree" network topology which can connect a plurality of microprocessors through an arrangement of crossbar switches (crossbar or crosspoint switches are described in a variety of references, e.g., Katz, Randy H., Contemporary Logic Design, Benjamin-Cummings Publishing, Redwood City, 1994, pp. 226-228).
In a fat tree, a crossbar switch can be positioned at each of a plurality of network nodes. Each crossbar switch can connect any of its "parent" ports with any of its "children" ports. Each port is the entry to a channel that includes an n-bit datapath (data, control and clocking). The switches are arranged in a series of ordered levels so that a switch in any one of the levels has data paths to the parent ports of a number of switches (e.g., four) in the next lower level and data paths to the children ports of a number of switches (e.g., two) in the next higher level. The microprocessors are coupled to the children ports of the lowest level.
Therefore, a plurality of data paths are available between any selected pair of microprocessors. Messages can be sent along various ones of these data paths simultaneously. Message priorities can be established to address situations in which two messages are routed along the same path portion. In this case, the message with the lower priority relinquishes the path portion to the other message.
Interconnection systems of the fat tree type are intended to reduce operation times by providing an abundance of component interconnection paths so that multiple processor pair connections can be made simultaneously. As a consequence, these systems are generally bulky because of their high parts count, e.g., a large number of crossbar switches. However, many interconnection applications, e.g., missiles and space vehicles, require that spatial volume be a prime consideration.